* {
    margin: 0;
    padding: 0;
}

html,
body {
    height: 100%;
    background-color: #fff;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}


.btn {
    margin-top: 30px;
}

.btn button {
    padding: 7px 13px;
    margin: 0 5px;
}

.grid {
    width: 450px;
    height: 450px;
    border: 1px solid #000;
    background-color: #f2f2f2;
}

@keyframes am {
    0% {
        border: 2px solid #1897ff;
    }

    100% {
        border: 2px dashed #1897ff;
    }
}

.grid.edit {
    border: 2px dashed #1897ff;
    /* animation: am 2s infinite linear; */
}

.grid .block {
    width: 50px;
    height: 50px;
    border: 1px solid #000;
    box-sizing: border-box;
    font-size: 18px;
    float: left;
    text-align: center;
    line-height: 50px;
}

.grid .block.fix {
    font-weight: bold;
}